Autoinflammatory & rare systemic diseases
Anti-C1q antibodies in IgG4-related disease are common and associated with renal involvement and cutaneous small-vessel vasculitis
Authors' conclusion
This study is the first to evaluate anti-C1q antibodies in IgG4-RD, finding a high prevalence, particularly in patients with renal involvement and CSVV.
Study context
- Population
- Patients with IgG4-related disease (IgG4-RD) meeting the revised 2020 Comprehensive Diagnostic Criteria and/or the 2019 ACR/EULAR Classification Criteria34 (48.6%) male
- Participants
- 70 patients
- Outcome
- Prevalence of anti-C1q antibodies (quantitative ELISA, cut-off <10 U/ml)
Main finding
As reported in the abstract
Anti-C1q antibody positivity
Anti-C1q antibodies positive
74.3%
Median anti-C1q level
19.8 U/ml
Observational data: associations, not effects.
Further findings
Anti-C1q levels, active vs inactive disease
- Higher anti-C1q levels in active than inactive disease
- P = 0.03
Renal involvement by anti-C1q status
- Renal involvement more frequent in anti-C1q positive patients
- P = 0.01
Cutaneous small-vessel vasculitis (CSVV)
- Patients with CSVV
- 6 (8.6%)
- All CSVV patients anti-C1q positive; all had palpable purpura; one had urticarial-like lesions
- Skin biopsies in 3 patients showed leukocytoclastic vasculitis with lymphocytic and eosinophilic infiltrates
Correlations of anti-C1q levels
- Negative correlation with C3 and C4; positive with IgG1, IgG4 and serum free light chains
Relapse-free survival
- Anti-C1q positivity did not predict relapse-free survival
Original publication
Anti-C1q antibodies in IgG4-related disease are common and associated with renal involvement and cutaneous small-vessel vasculitis. Rheumatology (Oxford). Published 11 January 2025. doi:10.
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